Decorator error when using @ variables in actions

[AprilArcus]

This error is produced on the current master, 396e9250c8afd5d7d7e5658951b0d89f8bd97dd9.

It appears that the legacy decorators plugin is being introduced here: https://github.com/GerHobbelt/recast/blob/master/parsers/_babel_options.ts#L29

It looks like a workaround was committed at 625fcce but that it hasn't yet been built into dist/cli-cjs.js

JisonParserError: 
production rule action code block does not compile: Leading decorators must be attached to a class declaration (64:66)
    
  Erroneous area:
63:     | end_of_file {
^^....................^
64:                 parser.addError(yy.myFunction(@$))
^^..^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
65:             }
^^..^^^^^^^^^^^^^
66:     ;
67: 

Related: #63